Pathology of Cancer
Cancer is characterized primarily by an increase in the number of abnormal cells derived from a given normal tissue, invasion of adjacent tissues by these abnormal cells, or lymphatic or blood-borne spread of malignant cells to regional lymph nodes and to distant sites (metastasis). Clinical data and molecular biologic studies indicate that cancer is a multistep process that begins with minor preneoplastic changes, which may under certain conditions progress to neoplasia. The neoplastic lesion may evolve clonally and develop an increasing capacity for invasion, growth, metastasis, and heterogeneity, especially under conditions in which the neoplastic cells escape the host's immune surveillance. Roitt, I., Brostoff, J and Kale, D., Immunology, 17.1-17.12 (3rd ed., Mosby, St. Louis, Mo., 1993).
There is an enormous variety of cancers which are described in detail in the medical literature. Examples include cancer of the lung, colon, rectum, prostate, breast, brain, and intestine. The incidence of cancer continues to climb as the general population ages, as new cancers develop, and as susceptible populations (e.g., people infected with AIDS or excessively exposed to sunlight) grow. However, options for the treatment of cancer are limited. For example, in the case of blood cancers (e.g., multiple myeloma), few treatment options are available, especially when conventional chemotherapy fails and bone-marrow transplantation is not an option. A tremendous demand therefore exists for new methods and compositions that can be used to treat patients with cancer.
Many types of cancers are associated with new blood vessel formation, a process known as angiogenesis. Several of the mechanisms involved in tumor-induced angiogenesis have been elucidated. The most direct of these mechanisms is the secretion by the tumor cells of cytokines with angiogenic properties. Examples of these cytokines include acidic and basic fibroblast growth factor (a,b-FGF), angiogenin, vascular endothelial growth factor (VEGF), and TNF-γ. Alternatively, tumor cells can release angiogenic peptides through the production of proteases and the subsequent breakdown of the extracellular matrix where some cytokines are stored (e.g., b-FGF). Angiogenesis can also be induced indirectly through the recruitment of inflammatory cells (particularly macrophages) and their subsequent release of angiogenic cytokines (e.g., TNF-α, b-FGF).
Vitamin D Agents and Cancer
In addition to their primary role in maintaining bone mineralization, vitamin D agents have been shown to be effective as inhibitors of tumor cell growth. For example, in breast cancer cell lines, inhibitory effects on cell cycle arrest, angiogenesis, invasion and metastasis have been observed in addition to pro-apoptotic effects. In addition, vitamin D agents have been shown to inhibit and prevent breast cancer growth in several mouse models, and a correlation between vitamin D receptor expression on breast cancer cells and disease free survival of breast cancer patients has also been observed.
Despite the beneficial effects of vitamin D agents, limitations such as development of vitamin D resistance by tumor cells and hypercalcaemia present challenges in using vitamin D agents in cancer therapy. Thus, restoration of vitamin D sensitivity in tumor cells that develop vitamin D resistance would be a valuable therapeutic tool in cancer treatment.
Immunomodulatory Compounds
A number of studies have been conducted with the aim of providing compounds that can safely and effectively be used to treat diseases associated with abnormal production of TNF-α. See, e.g., Marriott, J. B., et al., Expert Opin. Biol. Ther. 1(4):1-8 (2001); G. W. Muller, et al., Journal of Medicinal Chemistry 39(17): 3238-3240 (1996); and G. W. Muller, et al., Bioorganic & Medicinal Chemistry Letters 8: 2669-2674 (1998). Some studies have focused on a group of compounds selected for their capacity to potently inhibit TNF-α production by LPS stimulated PBMC. L. G. Corral, et al., Ann Rheum. Dis. 58:(Suppl I) 1107-1113 (1999). These compounds, which are referred to as IMiDs™ (Celgene Corporation) or Immunomodulatory Drugs, show not only potent inhibition of TNF-α but also marked inhibition of LPS induced monocyte IL1β and IL12 production. LPS induced IL6 is also inhibited by immunomodulatory compounds, albeit partially. These compounds are potent stimulators of LPS induced IL10. Id. Particular examples of immunomodulatory compounds include, but are not limited to, the substituted 2-(2,6-dioxopiperidin-3-yl) phthalimides and substituted 2-(2,6-dioxopiperidin-3-yl)-1-oxoisoindoles described in U.S. Pat. Nos. 6,281,230 and 6,316,471, both to G. W. Muller, et al.